ci: update el builders and force ompi v5.0.0rc2

[garlick]

Problem: builds are failing because the ompi v5.0.x branch now requires openpmix v4.2.2.

For the moment, reconfigure CI to lock in the ompi v5.0.0rc2 tag, which works with openpmix v4.1.1.

Thanks to @grondo for providing the patch to modernize the el builders also.

[codecov[bot]]

Codecov Report

Merging #64 (692ef9c) into main (44256f0) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #64   +/-   ##
=======================================
  Coverage   78.46%   78.46%           
=======================================
  Files          10       10           
  Lines        1189     1189           
=======================================
  Hits          933      933           
  Misses        256      256           

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